Referring to FIG. 10 and FIG. 11, the two figures respectively show a perspective view and an explored view of a back combined pogo pin 40. The pogo pin 40 comprises a barrel 41 having an opening (not shown) at the top thereof, a pin head 42 arranged in the barrel 41 and having a top end protruded out from said opening, a spring 43 arranged in the barrel 41, and a rear stopper 44 blocking the bottom of the barrel 41. The rear stopper 44 has a convex rib 441 enclosed around for closely binding the rear stopper 44 to the bottom of the barrel 41.
When assembling the pogo pin 40, the pin head 42 is penetrated into the barrel 41 and located at the top thereof. The spring 43 is inserted into the barrel 41, and then the rear stopper 44 is pushed into the barrel 41 from the bottom thereof and fastened thereto. In such a manner, the spring 43 can be compressed between the pin head 42 and the rear stopper 44, and the pin head 42 can be extended out from the barrel 41 and also can be retreated into the barrel 41. The above back combined pogo pin 40 is applied to various types of connectors with the retractable pin head 42. Therefore, there is a need to develop an assembly fixture capable of assembling the pogo pin 40 quickly.